There are some paints that can be used on the inside surface of your roof deck to block heat and lower the temperature of your attic on a hot day. These paints are usually silver or metallic in color and are designed to block IR solar radiation coming through a roof deck. The best performing of these paints can block up to 75% of the heat coming through the roof deck. Radiant barrier foil sheets can block 90-97% of heat through the roof, but the paint products may be easier to install, especially in retrofit situations. Be sure to find out the percentage of heat blockage for any product before you purchase. These paints are called Interior Radiation Control Coatings (IRCC).
Currently, EPA does not label paints and coating for the inside of roof decks (or attic) in the insulation program because paints and coatings do not meet the Federal Trade Commissions (FTC) definition of home insulation. EPA qualifies paint only as a roof coating in our Roofs program (generally used for the top of a commercial building roof). Roof coatings are NOT insulation. They reflect solar heat off a roof rather than absorbing it keeping the building cooler. EPA also qualifies radiant barrier insulation (a metallic foil material usually attached to a piece of wood and nailed to the inside roof deck) as ENERGY STAR because it meets the FTC definition of home insulation. For more information, see this technical study comparing the performance of several heat blocking paints in a simulated attic interior roof deck situation.